Stateless multicast in multi-domain networks

Abstract

Various example embodiments for supporting stateless multicast in communication networks are presented. Various example embodiments for supporting stateless multicast in communication networks may be configured to support stateless multicast in multi-domain packet distribution networks. Various example embodiments for supporting stateless multicast in communication networks may be configured to support stateless multicast in multi-domain packet distribution networks which may be based on Internet Protocol (IP). Various example embodiments for supporting stateless multicast in a multi-domain packet distribution network may be configured to support multicast of packets based on use of internal multicast packets for multicast communication of the multicast packets within sub-domains of the multi-domain packet distribution network and use of external multicast packets for unicast communication of the multicast packets across or between sub-domains of the multi-domain packet distribution network.

What is claimed is: 
     
       1. An apparatus, comprising:
 at least one processor; and 
 at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to:
 determine, by a node of a sub-domain of a network domain for a packet of a multicast flow, a set of egress nodes to which the packet is to be delivered; 
 determine, by the node from the set of egress nodes to which the packet is to be delivered, a set of external egress nodes that are located outside of the sub-domain and that are served by a common border node of the sub-domain, wherein the common border node of the sub-domain is a common egress point from the sub-domain for the external egress nodes and is a common node in respective shortest paths from the node to the external egress nodes; 
 generate, by the node based on the set of external egress nodes, a label switched packet including an encoding of an indication of the set of external egress nodes; and 
 send, by the node toward the common border node of the sub-domain based on unicast forwarding, the label switched packet. 
 
 
     
     
       2. The apparatus of  claim 1 , wherein the multicast flow is associated with a multicast group including a set of egress nodes for the multicast flow, wherein the node of the sub-domain is an ingress node of the sub-domain for the multicast flow, wherein the set of egress nodes to which the packet is to be delivered includes the set of egress nodes for the multicast flow. 
     
     
       3. The apparatus of  claim 2 , wherein the packet is generated by the ingress node of the network domain based on a packet of a multicast source for the multicast flow. 
     
     
       4. The apparatus of  claim 1 , wherein the multicast flow is associated with a multicast group including a set of egress nodes for the multicast flow, wherein the node of the sub-domain is a second border node of the sub-domain, wherein the set of egress nodes to which the packet is to be delivered includes a subset of the egress nodes for the multicast flow. 
     
     
       5. The apparatus of  claim 4 , wherein the packet is received by the second border node of the sub-domain via a unicast tunnel. 
     
     
       6. The apparatus of  claim 1 , wherein the set of external egress nodes is determined based on routing information maintained by the node. 
     
     
       7. The apparatus of  claim 6 , wherein the routing information includes, for each network node in a set of network nodes of the network domain, an indication as to whether the respective network node is internal to the sub-domain of the node or external to the sub-domain of the node. 
     
     
       8. The apparatus of  claim 7 , wherein the routing information includes, for each of the network nodes of the network domain that is external to the sub-domain of the node, an indication as to a border node with which the respective network node is associated and an address of the border node with which the respective network node is associated. 
     
     
       9. The apparatus of  claim 6 , wherein the routing information includes Internet Protocol (IP) based routing information. 
     
     
       10. The apparatus of  claim 1 , wherein the encoding of the indication of the set of external egress nodes includes a set of node identifiers identifying the respective external egress nodes. 
     
     
       11. The apparatus of  claim 1 , wherein, to send the packet, the instructions, when executed by the at least one processor, cause the apparatus to:
 forward, by the node toward the common border node via a unicast tunnel from the node to the common border node, the label switched packet. 
 
     
     
       12. The apparatus of  claim 11 , wherein the instructions, when executed by the at least one processor, cause the apparatus to:
 determine, by the node based on a list of preferred tunnel types associated with the common border node, a tunnel type of the unicast tunnel from the node to the common border node. 
 
     
     
       13. The apparatus of  claim 11 , wherein the unicast tunnel includes a Generic Routing Encapsulation (GRE) tunnel, a Multiprotocol Label Switching (MPLS) in User Datagram Protocol (MPLS-in-UDP) tunnel, an MPLS Label Switched Path (LSP), or an Interior Gateway Protocol (IGP) shortcut. 
     
     
       14. The apparatus of  claim 1 , wherein the instructions, when executed by the at least one processor, cause the apparatus to:
 determine, by the node from the set of egress nodes to which the packet is to be delivered, a set of internal egress nodes that are located inside of the sub-domain; 
 generate, by the node based on the set of internal egress nodes, a second label switched packet including an encoding of an indication of the set of internal egress nodes; and 
 send, by the node within the sub-domain based on multicast forwarding, the second label switched packet. 
 
     
     
       15. The apparatus of  claim 14 , wherein the encoding of the indication of the set of internal egress nodes includes a set of node identifiers identifying the respective internal egress nodes. 
     
     
       16. The apparatus of  claim 1 , wherein the instructions, when executed by the at least one processor, cause the apparatus to:
 maintain, by the node, a route table including a prefix field configured to indicate a route prefix, a next-hop field configured to indicate a next hop for the route prefix, a scope field configured to indicate whether a scope of the route prefix is internal to the sub-domain or external to the sub-domain, and a border node field configured to indicate a border node for the route prefix. 
 
     
     
       17. The apparatus of  claim 1 , wherein the instructions, when executed by the at least one processor, cause the apparatus to:
 maintain, by the node, a mapping table including a prefix field configured to indicate a route prefix, a next-hop field configured to indicate a next hop for the route prefix, a next-hop label field configured to indicate a label of the next hop for the route prefix, a scope field configured to indicate whether a scope of the route prefix is internal to the sub-domain or external to the sub-domain, a border node field configured to indicate a border node for the route prefix, and a border node label field configured to indicate a label of the border node for the route prefix. 
 
     
     
       18. The apparatus of  claim 1 , wherein the instructions, when executed by the at least one processor, cause the apparatus to:
 maintain, by the node, a border node tunnel table including an address field configured to indicate an address of a border node, a tunnel preference field configured to indicate a list of tunnel type preferences for tunneling from the node to the border node, and a resolved tunnel field configured to indicate a list of resolved unicast tunnels from the node to the border node. 
 
     
     
       19. The apparatus of  claim 1 , wherein the instructions, when executed by the at least one processor, cause the apparatus to:
 maintain, by the node, a mapping table including an incoming label field configured to indicate an incoming label received by the node, a next-hop field configured to indicate a next hop for the incoming label, a next-hop label field configured to indicate a label of the next hop for the incoming label, a scope field configured to indicate whether a scope of the incoming label is internal to the sub-domain or external to the sub-domain, a border node field configured to indicate a border node for the incoming label, and a border node label field configured to indicate a label of the border node for the incoming label. 
 
     
     
       20. The apparatus of  claim 1 , wherein the sub-domain includes a Shortest Path First (OSPF) area, an OSPF version 3 (OSPFv3) area, an Intermediate-System-to-Intermediate-System (IS-IS) level, or a Border Gateway Protocol (BGP) autonomous system (AS). 
     
     
       21. A method, comprising:
 determining, by a node of a sub-domain of a network domain for a packet of a multicast flow, a set of egress nodes to which the packet is to be delivered; 
 determining, by the node from the set of egress nodes to which the packet is to be delivered, a set of external egress nodes that are located outside of the sub-domain and that are served by a common border node of the sub-domain, wherein the common border node of the sub-domain is a common egress point from the sub-domain for the external egress nodes and is a common node in respective shortest paths from the node to the external egress nodes; 
 generating, by the node based on the set of external egress nodes, a label switched packet including an encoding of an indication of the set of external egress nodes; and 
 sending, by the node toward the common border node of the sub-domain based on unicast forwarding, the label switched packet. 
 
     
     
       22. An apparatus, comprising:
 at least one processor; and 
 at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to:
 receive, by a first border node associated with a first sub-domain and based on unicast forwarding, a first label switched packet including an encoding of an indication of a set of external egress nodes for which the first label switched packet is intended, wherein the external egress nodes belong to a multicast group and are disposed outside of the first sub-domain; 
 generate, by the first border node based on the first label switched packet, a second label switched packet, wherein the second label switched packet includes an encoding of an indication of a first subset of external egress nodes, from the set of external egress nodes, located within a second sub-domain; 
 forward, by the first border node toward a node of the second sub-domain based on multicast forwarding, the second label switched packet; 
 generate, by the first border node based on the label switched packet, a third label switched packet, wherein the third label switched packet includes an encoding of an indication of a second subset of external egress nodes, from the set of external egress nodes, located within a third sub-domain; and 
 forward, by the first border node toward a second border node associated with the second sub-domain and the third sub-domain and based on unicast forwarding, the third label switched packet.